1. Field of Invention
The present invention relates generally to the design and manufacturing of printed circuit boards. More particularly, the present invention relates to a plated through-hole that allows for multiple independent circuit connections to be made.
2. Description of the Related Art
Printed circuit boards are used in the formation of a wide variety of electrical devices. Typically, printed circuit boards include multiple layers of conductors, e.g., copper conductors, which are interconnected by metallized holes. Each metallized hole has plating that connects the layers of conductors exposed in the metallized hole to each other. For example, if three layers of a printed circuit board have conductors or traces through which the metallized hole passes, the three layers are interconnected. If a lead of an electrical component is inserted through a metallized hole, the plating in the metallized hole connects the layers of conductors exposed in the metallized hole to each other and to the electrical component.
As the circuit density on printed circuit boards increases, the need to efficiently utilize space on printed circuit boards is also increasing. Reducing the number of metallized holes in a printed circuit board will effectively free up the space on the printed circuit board for other purposes.
Using buried vias and backdrilling are methods which may allow the number of metallized holes used in a printed circuit board to be reduced. A buried via is generally a via that is embedded within a printed circuit board to connect a plurality of layers. Backdrilling allows plating of a metallized hole, e.g., stubs, to be removed such that the plating effectively terminates at a last conductive layer of a metallized hole. However, a buried via does not support more than one circuit connection therein, and backdrilling generally does not support more than one circuit connections in a metallized hole.
Therefore, what is needed is method and an apparatus that allows a metallized hole to support a plurality of independent circuit connections on different internal layers. That is, what is desired is a system which is suitable for providing multiple circuit connections or signal paths within a single, plated through-hole.